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Late Quaternary landscapes of unglaciated Beringia were largely shaped by ice-wedge polygon tundra. Ice Complex (IC) strata preserve such ancient polygon formations. Here we report on the Yukagir IC from Bol'shoy Lyakhovsky Island in northeastern Siberia and suggest that new radioisotope disequilibria (230Th/U) dates of the Yukagir IC peat confirm its formation during the Marine Oxygen Isotope Stage (MIS) 7a–c interglacial period. The preservation of the ice-rich Yukagir IC proves its resilience to last interglacial and late glacial–Holocene warming. This study compares the Yukagir IC to IC strata of MIS 5, MIS 3, and MIS 2 ages exposed on Bol'shoy Lyakhovsky Island. Besides high intrasedimental ice content and syngenetic ice wedges intersecting silts, sandy silts, the Yukagir IC is characterized by high organic matter (OM) accumulation and low OM decomposition of a distinctive Drepanocladus moss-peat. The Yukagir IC pollen data reveal grass-shrub-moss tundra indicating rather wet summer conditions similar to modern ones. The stable isotope composition of Yukagir IC wedge ice is similar to those of the MIS 5 and MIS 3 ICs pointing to similar atmospheric moisture generation and transport patterns in winter. IC data from glacial and interglacial periods provide insights into permafrost and climate dynamics since about 200 ka.
A lasting legacy of the International Polar Year (IPY) 2007–2008 was the promotion of the Permafrost Young Researchers Network (PYRN), initially an IPY outreach and education activity by the International Permafrost Association (IPA). With the momentum of IPY, PYRN developed into a thriving network that still connects young permafrost scientists, engineers, and researchers from other disciplines. This research note summarises (1) PYRN’s development since 2005 and the IPY’s role, (2) the first 2015 PYRN census and survey results, and (3) PYRN’s future plans to improve international and interdisciplinary exchange between young researchers. The review concludes that PYRN is an established network within the polar research community that has continually developed since 2005. PYRN’s successful activities were largely fostered by IPY. With >200 of the 1200 registered members active and engaged, PYRN is capitalising on the availability of social media tools and rising to meet environmental challenges while maintaining its role as a successful network honouring the legacy of IPY.
Short chain l-3-hydroxyacyl CoA dehydrogenase
(SCHAD) is a soluble dimeric enzyme critical for oxidative
metabolism of fatty acids. Its primary sequence has been
reported to be conserved across numerous tissues and species
with the notable exception of the pig heart homologue.
Preliminary efforts to solve the crystal structure of the
dimeric pig heart SCHAD suggested the unprecedented occurrence
of three enzyme subunits within the asymmetric unit, a
phenomenon that was thought to have hampered refinement
of the initial chain tracing. The recently solved crystal
coordinates of human heart SCHAD facilitated a molecular
replacement solution to the pig heart SCHAD data. Refinement
of the model, in conjunction with the nucleotide sequence
for pig heart SCHAD determined in this paper, has demonstrated
that the previously published pig heart SCHAD sequence
was incorrect. Presented here are the corrected amino acid
sequence and the high resolution crystal structure determined
for pig heart SCHAD complexed with its NAD+
cofactor (2.8 Å; Rcryst = 22.4%,
Rfree = 28.8%). In addition, the peculiar
phenomenon of a dimeric enzyme crystallizing with three
subunits contained in the asymmetric unit is described.
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